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KS4 Physics
Earth and Beyond
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Contents
Earth and Beyond
The solar system
The life cycles of stars
In orbit
The Universe
Summary activities
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Nuclear fusion
In nuclear fusion reactions, lighter
atomic nuclei are joined together
(fused) to form heavier atomic nuclei.
This process releases massive
amounts of energy.
In our Sun, a typical star, hydrogen is
being fused to form helium. This
provides the energy for life on Earth.
When all the hydrogen is used up, other elements will be
fused together to make even heavier elements.
Not all elements are made in this way. The heaviest
elements, some of which are found in your body, can only
be made when stars explode.
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The Sun as our energy source
The Sun is the source of energy for life on Earth.
Where does this energy come from?
The Sun is powered by nuclear fusion reactions.
Atomic nuclei are joined together (fused) due to
the very high pressures inside the Sun.
What would happen on Earth if the Sun suddenly
disappeared?
There would be no light, all plants would die (no
photosynthesis), all animals would die (no food
source) and temperatures would drop. It would lead
to the end of all life on Earth!
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Contents
Earth and Beyond
The solar system
The life cycles of stars
In orbit
The Universe
Summary activities
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The life cycles of stars
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Small stars
Lighter stars, like our Sun, follow this life cycle:
Nebula
collapses due
to its own
gravity.
Very small nebulae
form failed stars.
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Forms a
star like
our Sun.
Expands
to form a
red giant.
Outer layers of star
drift away to leave a
dense white dwarf.
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Massive stars
Stars that are much heavier than our Sun follow this life cycle:
Forms a star
more massive
than our Sun.
Larger nebula
collapses due to its
own gravity.
Expands
to form a
massive red
giant.
Red giant
collapses violently
in a supernova
explosion.
Very dense
neutron star
formed.
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Really massive stars
The end of the life cycle of really massive stars is different to
that of massive stars.
After a really massive red giant collapses in a supernova
explosion, it leaves a star so dense that not even light can
escape its gravitational pull. This is called a black hole!
Some scientists believe
that there are black
holes at the centre of
galaxies.
If light cannot escape a
black hole, then how can
a black hole be observed?
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Black holes
How can a black hole be observed?
A black hole cannot be seen directly and even if it could it
wouldn’t be black!
A black hole is ‘seen’ by observing the effect it has on
nearby matter.
If there is a star nearby,
matter from the star will
spiral into the black hole
and as it does so the
matter emits X ray
radiation which can be
detected.
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X rays
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Birth of a star
What is the correct order for these sentences about how a
star is formed?
This causes the
‘nebula’ to collapse.
Gravity causes a dust and
gas cloud to condense
into a smaller volume.
As the nebula collapses,
temperatures and pressures
inside the nebula increase.
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When the temperature and
pressure are great enough
nuclear fusion starts.
Eventually gravity and
the outward pressure
of escaping energy is
balanced. At this stage,
it is called a star.
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Comparing the life cycles of stars
Use these words below to complete the life cycles of
different stars:
small
nebula
white
dwarf
star larger
than our Sun
red giant
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large
nebula
nebula
massive
red giant
neutron
star
star like
our Sun
supernova
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Comparing the life cycles of stars
small
nebula
nebula
large
nebula
star like
our Sun
star larger
than our Sun
red giant
massive
red giant
white
dwarf
supernova
neutron
star
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Questions about stars
1. What two elements make up most of our Sun?
hydrogen and helium
2. What is a nebula?
A huge cloud of gas and dust from which a star is born.
3. What process has allowed the Sun to emit light and heat
radiation over billions of years?
nuclear fusion
4. Which is the most dense, a white dwarf or a neutron star?
neutron star
5. Describe the possible fate of a star similar to our Sun.
 red giant  white dwarf
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Contents
Earth and Beyond
The solar system
The life cycles of stars
In orbit
The Universe
Summary activities
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Orbiting the Sun
1. What force keeps the planets in orbit around the Sun?
the Sun’s gravity
2. Which planet shown will feel this force…
a) …the strongest?
b) …the weakest?
not to scale
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Questions about satellites
1. What are the two types of satellite?
natural and artificial
2. Give an example of each type?
natural – the Moon
artificial – navigation, spy, military,
weather, communications
3. Why are certain satellites, such as the Hubble Space
Telescope, put into space?
To view the Universe above the Earth’s
atmosphere which can obstruct view from Earth.
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Artificial satellites – different orbits
geostationary orbit
Satellite stays above the
same location on the
Earth’s surface. This
means that the speed
of its orbit matches the
Earth’s rotation.
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polar orbit
The satellite’s orbit passes
over the poles, whilst the Earth
spins underneath. This allows
large areas of Earth to be seen
and is used for mapping and
weather monitoring.
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Comparing orbits
Complete this the table comparing the different types
of orbits that artificial satellites can follow?
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Polar
Geostationary
Height of orbit
low
high
Orbital speed
fast
slow
Orbits per day
3-4
1
Orbit position
over poles
above equator
Example
weather
communications
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Which type of orbit?
Do these uses of satellites involve a polar orbit or a
geostationary orbit?
communications
spy
weather
navigation
monitoring ocean
temperatures
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geostationary
polar
polar and geostationary
geostationary
polar
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Contents
Earth and Beyond
The solar system
The life cycles of stars
In orbit
The Universe
Summary activities
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Size in the Universe
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Matching words and definitions
a star
a planet
Our Sun is one.
a galaxy
Billions of stars together - ours
is called the Milky Way.
the Universe
the Solar
System
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There are nine of these in our
Solar System. The Earth is one.
The Sun, planets, moons,
asteroids and comets make up
this.
All the galaxies and everything
else.
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Identify the different bodies
a galaxy
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a star
the Universe
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The Doppler effect
Think about the noise a plane makes as it passes you.
As the plane approaches,
it sounds higher pitched...

…as it moves away from you,
it sounds lower pitched.
This apparent shift in frequency is called the Doppler effect.
The same thing happens with light:
 The wavelength of light emitted by approaching
objects appears to be shortened (blue-shifted);
 The wavelength of light emitted by receding objects
appears to be increased (red-shifted).
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Hubble and the expanding Universe
Edwin Hubble (1889-1953) was a famous scientist who
examined the light from nearby galaxies. He made two
important observations:
1. That most of the galaxies’ light was shifted towards the
red end of the spectrum;
2. The further away a galaxy was, the more its light was
red-shifted.
From his observations, Hubble made these conclusions:
1. That most galaxies were moving away from our own;
2. The further away a galaxy was, the faster it was moving
away from us;
3. That the Universe must be expanding.
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The big-bang theory
The big-bang theory states that the Universe is expanding
due to a large ‘explosion’ (big bang) billions of years ago.
Evidence to support this theory includes:
1. The Cosmic Microwave Background Radiation (CMB),
which is thought to be an ‘echo’ of the initial explosion.
2. Hubble’s observations about red-shifted light.
This theory gives rise to different fates for the Universe:
1.If the mass of the Universe is large enough, it will eventually
start to contract due to gravity – closed Universe.
2.If the mass of the Universe is smaller, it will expand forever
as there is not enough gravity to halt its expansion – open
Universe.
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Steady state theory
The steady state theory states that the Universe is
expanding and, as it expands, matter is created to maintain
a uniform universal density of matter.
Evidence to support this theory is Hubble’s observations
about red-shifted light.
However, the steady state theory has become less popular
since the discovery of Cosmic Microwave Background
Radiation (CMB).
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Are we alone?
There are many different opinions about life in the Universe:
For life to exist there


  must be liquid water,
on a planet or moon
and oxygen.
The Universe is so big,
 We are all aliens, life
even if there are aliens,

began on comets and
they are too far away for
asteroids and transferred

us to ever meet them.
to the Earth when they
collided with it.
Life exists on Earth

and only on Earth.
There are 10 stars in the
 universe. There must be
If there are aliens they
If there are aliens,
they would have
contacted us by now.
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will probably not look
like you or me.
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
life on planets around
some of them.
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Is there life out there?
Many people believe that we are not the only intelligent life
in the Universe.
The challenge for scientists is to find evidence of other life.
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Contents
Earth and Beyond
The solar system
The life cycles of stars
In orbit
The Universe
Summary activities
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© Boardworks Ltd 2005
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Glossary (1)
 black hole – An object in space that forms after a really
massive star collapses in a supernova. Its gravity is so
strong that nothing can escape its pull.
 comet – A lump of rock and ice which has a very elliptical
orbit around the Sun.
 galaxy – A vast collection of billions of stars.
 geostationary orbit – The path of a satellite that stays
above the same position on the Earth’s surface and orbits at
the same speed as the Earth rotates.
 meteor – A lump of material from space that burns up in
the Earth’s atmosphere.
 meteorite – A large meteor that does not completely burn
up in the Earth’s atmosphere and crashes to Earth.
 nebula – A massive cloud of gas and dust in which a star
is formed.
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Glossary (2)
 neutron star – The very dense core that remains after a
massive red giant collapses in a supernova.
 nuclear fusion – The process in which lighter atomic
nuclei are joined together to form heavier atomic nuclei and
a massive amount of energy is released.
 polar orbit – The path of a satellite which passes over the
North and South poles.
 satellite – Any object that is in orbit around a larger object.
 red giant – A star that has expanded and has a red glow.
 supernova – The huge explosion that occurs when a
massive red giant is at the end of its life.
 white dwarf – The core that remains after the outer layers
of a small red giant drift away.
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Anagrams
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Multiple-choice quiz
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